Some good suggestions are the slingshot channel of that ingenious German, Joerg “Let me show you its features ho-ho-ho” Sprave:
The great astronomy channel with daily updates of Anton Petrov:
PBS Spacetime for those that are more into physics:
Be warned: A lot of their videos can cause quite the “oh my, I should replay this minute to get what he said” moments.
Brew:
The MozART group for some funny and good music:
https://www.youtube.com/channel/UCVgvS7VUBt5JHxCEgI6LhgA
Curious Droid for some very nice scientific topics and questions
Bright insight if you want a “alternative history” channel without the tinfoil silliness (he has some amazing info and photos in his videos and whether someone find what he says plausible or not is neither here or there. )
SciManDan a channel dedicated to debunking tinfoilers and flatearthers (very funny, but bring a helmet along to protect yourself from the facepalms. Some of the people he covers are totally bananas)
And last but not least the LockPickingLawyer … a channel that will make you never feel safe at home anymore 
(seriously, sometimes it takes him more time to explain what lock is infront of him, than actually pick the lock)
I mean look at this. The title is not even clickbait 
: